Exploring, drilling and completing hydrocarbon and other wells are generally complicated, time consuming and ultimately very expensive endeavors. As such, tremendous emphasis is often placed on well access in the hydrocarbon recovery industry. That is, access to a well at an oilfield for monitoring its condition and maintaining its proper health is of great importance in the industry. As described below, such access to the well is generally provided by a well access line accommodated by a drum positioned at the oilfield.
During monitoring and maintaining of a well, a host of oilfield equipment may be located at the oilfield near the well. As indicated, one such piece of equipment may be a drum assembly accommodating a well access line. The well access line itself is generally a wireline cable or slickline configured to secure a well tool at a downhole end thereof. Alternatively, the drum may be a “reel” of coiled tubing line capable of delivering a fluid therethrough and to the well. In the case of coiled tubing, the line may be threaded through an injector arm and into the well, whereas the more conventional wireline or slickline may be dropped into the well from a mast over the well. Regardless, several thousand feet of line may ultimately be deployed from the drum and delivered into the well, thereby providing well access for a variety of well monitoring and maintenance procedures.
Unfortunately, the several thousand feet of line wrapped about the drum assembly tends to take its toll on the drum. That is, the drum may be subjected to the pressure or load of the line itself simply by having the line wrapped thereabout. Additionally, over the course of well access operations as described above, tension on the line may increase the load on the drum. This may particularly be the case when the drum is directed by a winch to pull the line in an uphole direction, for example, at the conclusion of an operation. In such circumstances, the line may face obstacles which impede the uphole movement thereof, such as obstructions or bends in the well architecture. Regardless, when such obstacles are presented, the load imparted on the drum through the increase in tension on the line may be quite significant.
Drums for well access operations, such as wireline operations, are generally constructed to withstand significant amounts of load. Nevertheless, the cumulative effects of such high tension and resulting high load as noted above may lead to plastifying of the drum, which may leave the drum ineffective for proper use in well access operations. The drum is particularly susceptible to plastifying of this nature at a junction of its core, about which the line is wrapped, and the wall-like flanges at the sides thereof, which help to retain the line in position about the core. Unfortunately, once rendered ineffective in this manner, the drum may be replaced at a cost that is often in excess of $80,000 or more in today's dollars.
Furthermore, the frequency of drum replacement for well access operations has risen sharply in the last several years and is likely to continue rising. This is a result of the sophisticated wells which are becoming more and more common. That is, in today's hydrocarbon recovery industry, deeper and deeper wells are regularly employed which require a greater amount of line for access. In some cases, the line may exceed 30,000 feet or more. This naturally places a greater amount of load on the drum from the outset, even before any of the line is deployed. Additionally, highly deviated and tortuous wells are becoming more and more common. As a result, the tension of the line on the drum is increased due to the added amount of friction and fluid resistance that accompany wells of such complicated architecture. All in all, the life expectancy of a conventional drum regularly employed in such high tension operations is significantly reduced.
Efforts have been made to minimize the load imparted on the drum during a given well access operation. One such effort is to employ an expected tension or load profile which is established in advance of the operation. So, for example, in the case of a particularly tortuous well, retrieval of the line may proceed in a manner that accounts for a toolstring rounding a bend in the well or other predictable occurrences that may be accounted for by the profile. Thus, the parameters of the retrieval may be adjusted to account for the line pulling the toolstring equipment around the bend.
Unfortunately, many of the factors which lead to an increase in tension on the line may not be built into an expected load profile. That is, much of what causes tension on the line is a matter of the ‘unexpected’. For example, the expected load profile would not account for unknown obstructions or unexpected changes in pressure that result in differential sticking. Thus, advance warning is not always available. Furthermore, there remains an absence of real-time drum load monitoring to address this issue. This is due to mechanical interfacing challenges presented by the prospect of directly monitoring a load on a rotating drum. Additionally, in circumstances where the drum does make it through the operation in spite of concerns over potentially exceeded load thresholds, other concerns remain. For example, due to the lack of direct drum load information, no reliable load history is preserved for the drum. As a result, rather than risk a catastrophic event during operation, the drum is most likely discarded after a given number of uses irrespective of its actual structural condition.